1. Technical Field
Embodiments of the invention relate generally to the field of semiconductor technology and, more particularly, to removal of surface defects using laser ablation methods.
2. Description of Related Art
A key requirement for microelectronics products, such as processor dice, intended for the consumer sector is the visual appearance of the products to be marketed. Very often, consumers place equal importance on the performance as well as the appearance of the products. Surface defects that are clearly distinguishable may impair a performance perception of the product, thereby leading to a possible loss of sales.
Surface defects may be introduced at various stages of the semiconductor manufacturing and assembly process. For example, etch pits may appear on the backside surface of a silicon wafer after micro-fabrication processes such as etching. Scratch marks may be introduced to die back side and edge at the sorting stage. Scuff marks may be introduced to the back side metallization (BSM) layer deposited on a bare die at a die-level-cherry-picking (DLCP) testing stage. These, and other various processes, increase the propensity of surface defects, resulting in an average yield loss of around 1% to around 3%.
Current methods for removing the visual defects from semiconductor assemblies include grinding the backside surface of the silicon wafer prior to deposition of a BSM layer, and roughening or polishing a die package surface at pre/post testing stage. These methods, however, are unable to provide satisfactory removal of all the surface defects. For example, grinding may remove defects introduced during fabrication stage but may not remove defects introduced during testing stage at End of Line (EOL). In view of the foregoing problems, improved methods for removing surface defects from the semiconductor assemblies are desired.